Some car paints include tiny flakes of silica, $\text{SiO}_2$. In the solid structure of $\text{SiO}_2$: • each silicon atom is bonded to $x$ oxygen atoms, • each oxygen atom is bonded to $y$ silicon atoms, • each bond is a $z$ type bond. What is the correct combination of $x$, $y$ and $z$ in this statement?
- A$x = 2$, $y = 1$, $z =$ covalent
- B$x = 2$, $y = 1$, $z =$ ionic
- C$x = 4$, $y = 2$, $z =$ covalent
- D$x = 4$, $y = 2$, $z =$ ionic